A double surfaced, internal crossbar hang glider design followed the Aolus, called the Sonic.

The 1981 Aolus was the first version of this planform from Spectra Aircraft, by design engineer Carlos Moralles. It had a wide 150 degree nose angle to minimize spanwise flow and maximize span efficiency. The tail was added to provide for pitch stability which would be lost due to the minimal sweep in the wings.

The Aolus was available in three sizes: 150, 170, and 190.

It has been described as “pitch weird and yaw funky. Tests had shown the washout tubes to have no needed pitch effect, but that they were put on for pilot expectations. Assembly was flat on the ground, with tricky ways of getting that high tension sweep cable/bow sprit in place.

In 1981 Carlos Miralles taught flying on the second prototype off Cuesta Ridge in San Luis Obispo, California, and sold it for $500.

It was a superb thermalling machine. In a strong, smooth core, you could push out past stall and flat-spin at 2000 fps. With that reflexed tail, it gave you a very secure feeling that it would recover from going over the falls in violent thermals. And fast landings in high-altitude-density air were helped by that bowsprit. When it dropped, you’d fly through the bars and hit the sail (no crossbar). But the thing that made the Aolus such a great thermalling machine, that huge tail, may have kept it from attaining the best l/d between thermals.